1. Field of the Invention
The present invention relates to a crawler travel unit mountable on a rear portion of a tractor or the like.
2. Description of Related Art
As a crawler travel unit, there can be mentioned those used in a semi-crawler tractor, in which the unit is installed as a rear wheel tire of the tractor, or replaceable with a rear wheel tire.
In the prior art of the crawler travel unit of this type, for example, as disclosed in Patent document 1, a front driven wheel for adjusting tension, a driven wheel which loosely rotates and idling wheels therebetween are aligned in a front-rear direction and supported by a track frame; a drive wheel is arranged upward of the idling wheels; a crawler track is wrapped around all of these wheels; a tension adjusting mechanism for supporting the front driven wheel and biasing the same in a direction that adjusts tension is sloping downward from the track frame to the front driven wheel; the track frame is made swingable about an axis which is in parallel with an axis of the drive wheel and positioned downward of the axis; a swing range regulating means for setting a swing range of the track frame is disposed on a driven wheel side relative to the swing axis; the front driven wheel, driven wheel and idling wheels are supported by respective support shafts cantilevered outward from the track frame; and at least the support shaft of the idling wheel is sloping outward and downward.
Three idling wheels arranged in a front-rear direction are separately supported by the track frame through the respective wheel shafts.    Patent document 1: Japanese Patent JP3560893B